When I first heard the term ‘carbon sequestration’, I had to look it up in the dictionary. What does ‘sequestration’ mean? In normal English, ‘sequester’ means to isolate; in chemistry terms, it means to make a substance inert by forming other stable compounds with it so that it is no longer available for reactions. While ‘carbon sequestration’ seems to imply absorption of carbon dioxide in many contexts, it is more than that. The carbon part of carbon dioxide should be used to form other compounds so that it will not form greenhouse gases that will cause climate change.
As we have seen from the previous articles, carbon dioxide (CO2) is the most prevalent greenhouse gas (GHG) in the atmosphere besides water vapour. Methane (CH4) is another carbon compound that contributes to the warming effect of the planet. To mitigate climate change, mankind needs to avoid and reduce emissions and remove GHG from the atmosphere. Avoiding and reducing emissions means keeping carbon in its original form (e.g. hydrocarbon molecule in petroleum underground, wood fibre in trees) and not letting it become carbon dioxide, methane or other greenhouse gases; failing which, if greenhouse gases are formed, stopping them from entering the atmosphere. Removing greenhouse gases already present in the atmosphere is another option. Greenhouse gases arrested or removed will need to be stored or sequestered.
Emissions reduction can be achieved via technology-based or nature-based pathways. Technology pathways include changing primary energy sources from fossil fuels to renewable energy, changing industry processes so that greenhouse gas-producing reactions will not be used, changing equipment and appliances to energy-saving ones, capturing methane from palm oil mills, waste management facilities, etc. It also includes the latest buzzword in Sarawak – carbon capture and storage (CCS) or carbon capture, utilisation and storage (CCUS).
Renewable energy includes solar, hydro, wind, geothermal, ocean and biomass energy.
Solar energy refers to solar thermal energy (solar water heaters for residential or commercial buildings or solar steam generators for industrial use) or photovoltaic (solar panels) that convert sunlight directly into electricity. Solar panels are now seen on rooftops as well as large-scale solar farms.
While in the olden days, watermills were used to capture the power of running water, modern-day hydropower mainly refers to hydroelectric power. It can be harnessed using power plants with electric turbines connected to dams and reservoirs that provide water on demand or run-of-river plants that do not have on-demand capability. Sarawak is blessed with large rivers with high potential for hydroelectricity. Currently, there are three hydroelectric plants with reservoirs and dams in Sarawak: Batang Ai, Bakun and Murum. The fourth one, Baleh, is scheduled to come on stream in 2028.
Wind energy is harnessed with windmills. Not many windmills are seen in Malaysia because most places onshore do not enjoy high wind speed.
Geothermal energy produced by the earth’s interior can be harnessed by drilling wells in areas with hot springs, piping hot water to heat the onsen spa, or piping hot steam to turn turbines that generate electricity.
Ocean energy or marine energy comes in different forms. Wave or tidal movement can be used to turn turbines. Differences in salinity between seawater and river water can be used to generate osmotic power. The thermal gradient between surface water and deep ocean water is also an energy source. However, technologies for ocean energy are not so mature yet.
As organic waste decomposes, methane is usually generated. Large amounts of methane are generated from palm oil mill effluent, farm waste and landfill facilities. With proper infrastructure called an anaerobic digestor, methane or biogas can be captured and stored until it is used as fuel in situ or piped to other gas consumers using natural gas pipelines.
Carbon capture and storage (CCS) normally refers to the geological storage of carbon dioxide. Carbon dioxide is isolated, purified, dewatered, compressed, and transported to a storage site, where it is pumped into underground rock layers via injection wells. The storage rock layers (saline aquifers or depleted oil and gas reservoirs) are selected and managed to effectively keep carbon dioxide under high pressure, thus immobilizing it. Malaysia is blessed with favourable geological conditions to potentially store 9 billion metric tons of carbon dioxide equivalent (tCO2e).
Removing carbon dioxide from the atmosphere can be done via expensive technology. Direct air capture needs large facilities and a lot of energy to pump air through chemical-based carbon dioxide absorbers and to isolate carbon dioxide for storage or sequestration. It is estimated that direct air capture technology currently costs between $230 and $540 per tCO2e. If we were to remove all the GHG that we release into the atmosphere (estimated at 57,400,000 tCO2e globally in 2022) with direct air capture technology, it would cost USD3 trillion at the current technology cost, not including the land space that it would take up and the infrastructure cost.
Surely that’s too expensive! Fortunately, there is another pathway for carbon removal and sequestration – nature-based solutions (NBS). With photosynthesis, plants absorb carbon dioxide from the atmosphere and turn it (sequester it) into roots, trunks, leaves, flowers and fruits. Sarawak is blessed with dense tropical moist forests with multiple storeys of vegetation (in the forest floor, shrub and herb, understorey, canopy and emergent layers) that store vast amounts of carbon.
Fallen leaves, flowers, fruits, branches and tree trunks decompose and release carbon dioxide and methane back into the atmosphere, except when they fall into water-logged peat swamp or mangrove ecosystems that slows the decaying process and store them as organic matter in peat and mangrove soils. Sarawak hosts 70% of peatlands and 26% of mangroves in Malaysia. It is important to preserve these carbon sinks that sequester carbon and reduce emissions of GHG into the atmosphere.
Calcifying corals sequester 70-90 Mg ton CO2 yearly by forming calcium carbonate (CaCO3) around their bodies in the ocean. Planting more trees and propagating more corals means more carbon dioxide can be removed from the air, and that will not cost USD 1,000/tCO2e.
The views expressed here are those of the writer and do not necessarily represent the views of the New Sarawak Tribune.
